/** @file  ../include/string.h

@internalComponent

*/

/** @fn  memccpy(void *t, const void *f, int c, size_t n)

@param t

@param f

@param c

@param n

@return   memccpy function returns a pointer to the next character in t after c, or NULL if c was not found in the first n characters of f.

  The memccpy function

copies bytes from string f to string t. If the character c (as converted to an unsigned char) occurs in the string f, the copy stops and a pointer to the byte after the copy of c in the string t is returned.

Otherwise, n bytes are copied, and a NULL pointer is returned.

Examples:

@code

#include <string.h>

#include <stdio.h>

int main()

{

    char one[50] = {"\0"};

    (void) memccpy(one, "abcdefgh",8,3);

    printf("String after memcpy %s

",one);

    (void) memccpy(one, "Hello",5,1);

    printf("String after memcpy %s

",one);

    return 0;

}

@endcode

 Output

@code

String after memcpy abc

String after memcpy Hbc

@endcode

@see bcopy()

@see memcpy()

@see memmove()

@see strcpy()

@publishedAll

@externallyDefinedApi

*/

/** @fn  memchr(const void *s, int c, size_t n)

@param s

@param c

@param n

@return   The memchr function

returns a pointer to the byte located,

or NULL if no such byte exists within n bytes.

  The memchr function

locates the first occurrence of c (converted to an unsigned char)

in string s.

Examples:

@code

#include <string.h>

#include <stdio.h>

int main()

{

    char one[50];

    char* ret;

    strcpy(one,"abcd");

    ret = memchr("abcd", ’c’,4);

    if(!strncmp(one+2,ret,1)) printf("\ ’c\ ’ found in string \"abcd\"\n");

    ret = memchr(one, ’z’,4);

    if(ret == NULL) printf("\ ’z\ ’ not found in string \"abcd\"\n");           

    return 0;

}

@endcode

 Output

@code

 ’c’ found in string "abcd"

 ’z’ not found in string "abcd"

@endcode

@see strchr()

@see strcspn()

@see strpbrk()

@see strsep()

@see strstr()

@see strtok()

@publishedAll

@externallyDefinedApi

*/

/** @fn  memcmp(const void *s1, const void *s2, size_t n)

@param s1

@param s2

@param n

@return   The memcmp function

returns zero if the two strings are identical,

otherwise returns the difference between the first two differing bytes

(treated as unsigned char values, so that '\\200'

is greater than '\\0'

for example).

Zero-length strings are always identical.

  The memcmp function

compares byte string s1 against byte string s2. Both strings are assumed to be n bytes long.

Examples:

@code

#include <string.h>

#include <stdio.h>

int main()

{

   char str1[]  = "abcdefg";

   char str2[] =  "abcdefr";

   int result;

   printf( "Compare ’%.6s’ to ’%.6s\n", str1, str2 );

   result = memcmp( str1, str2, 6);

   if( result < 0 )

      printf( "str1 is less than str2.\n" );

   else if( result == 0 )

      printf( "str1 is equal to str2.\n" );

   else if( result > 0 )

      printf( "str1 is greater than str2.\n" );

   printf( "Compare ’%.7s’ to ’%.7s\n", str1, str2 );

   result = memcmp( str1, str2, 7 );

   if( result < 0 )

      printf( "str1 is less than str2.\n" );

   else if( result == 0 )

      printf( "str1 is equal to str2.\n" );

   else if( result > 0 )

      printf( "str1 is greater than str2.\n" );

   return 0;    

}

@endcode

 Output

@code

Compare ’abcdef’ to ’abcdef

str1 is equal to str2.

Compare ’abcdefg’ to ’abcdefr

str1 is less than str2.

@endcode

@see bcmp()

@see strcasecmp()

@see strcmp()

@see strcoll()

@see strxfrm()

@publishedAll

@externallyDefinedApi

*/

/** @fn  memcpy(void *dst, const void *src, size_t len)

@param dst

@param src

@param len

@return   The memcpy function

returns the original value of dst.

  The memcpy function

copies len bytes from string src to string dst.

Examples:

@code

#include <string.h>

#include <stdio.h>

int main()

{

    char one[50] = {"\0"};

    (void) memcpy(one, "abcdefgh",8);

    printf("String after memcpy %s

",one);

    (void) memcpy(one, "Hello",5);

    printf("String after memcpy %s

",one);

    return 0;   

}

@endcode

 Output

@code

String after memcpy abcdefgh

String after memcpy Hellofgh

@endcode

@see bcopy()

@see memccpy()

@see memmove()

@see strcpy()

@publishedAll

@externallyDefinedApi

*/

/** @fn  memmove(void *dst, const void *src, size_t len)

@param dst

@param src

@param len

  The memmove function copies len bytes from string src to string dst. The two strings may overlap. The copy is always done in a non-destructive 

manner.

Examples:

@code

#include <string.h>

#include <stdio.h>

int main()

{

    char one[50];

    (void) strcpy(one, "abcdefgh");

    printf("String before memmove %s

",one);

    (void) memmove(one+1, "xyz", 2);

    printf("String after memmove %s

",one);

    (void) strcpy(one, "abcdefgh");

    printf("String before memmove %s

",one);

    (void) memmove(one+1, "xyz", 0);

    printf("String after memmove %s

",one);

    return 0;   

}

@endcode

 Output

@code

String before memmove abcdefgh

String after memmove axydefgh

String before memmove abcdefgh

String after memmove abcdefgh

@endcode

@return   The memmove function returns pointer to dst dst.

@see bcopy()

@see memcpy()

@see strcpy()

@publishedAll

@externallyDefinedApi

*/

/** @fn  memset(void *dst0, int c0, size_t length)

@param dst0

@param c0

@param length

  The memset function

writes length bytes of value c0 (converted to an unsigned char) to the string dst0.

Examples:

@code

#include <string.h>

#include <stdio.h>

int main()

{

    char one[50];       

    strcpy(one, "abcdefgh");

    printf("String before memset %s

",one);

    memset(one+1, 'x', 3);

    printf("String after calling memset first time %s

",one);          

    memset(one+2, 'y', 0);

    printf("String after calling memset second time %s

",one);

    return 0;   

}

@endcode

 Output

@code

String before memset abcdefgh

String after calling memset first time axxxefgh

String after calling memset second time axxxefgh

@endcode

@return   The memset function returns its first argument.

@see bzero()

@see swab()

@publishedAll

@externallyDefinedApi

*/

/** @fn  stpcpy(char *to, const char *from)

@param to

@param from

Note: This description also covers the following functions -

 strcpy()  strncpy() 

@return   The strcpy and strncpy functions

return to. The stpcpy function returns a pointer to the terminating ‘\\0’

character of to.

  The stpcpy and strcpy functions

copy the string from to to (including the terminating ‘\\0’

character.)

 The strncpy function copies at most len characters from from into to. If from is less than len characters long,

the remainder of to is filled with '\\0'

characters.

Otherwise, to is not terminated.

Examples:

@code

#include <string.h>

#include <stdio.h>

int main()

{

    char one[50] = {"abcdefgh"};        

    printf("String before strcpy %s

",one);

    strcpy(one,"Hello");

    printf("String after strcpy %s

",one);

    strncpy(one + 5, " ",1);

    strncpy(one + 6, "World",5);

    printf("String after strncpy %s

",one);

    return 0;   

}

@endcode

 Output

@code

String before strcpy abcdefgh

String after strcpy Hello

String after strncpy Hello World

@endcode

Examples:

 The following sets chararray to "abc\\0\\0\\0"

@code

char chararray[6];

(void)strncpy(chararray, "abc", sizeof(chararray));

@endcode

 The following sets chararray to "abcdef:"

@code

char chararray[6];

(void)strncpy(chararray, "abcdefgh", sizeof(chararray));

@endcode

 Note that it does not NULL terminate chararray because the length of the source string is greater than or equal

to the length argument. The following copies as many characters from input to buf as will fit and NULL terminates the result.

Because strncpy does not guarantee to NULL terminate the string itself, this must be done explicitly.

@code

char buf[1024];

(void)strncpy(buf, input, sizeof(buf) - 1);

buf[sizeof(buf) - 1] = ’\0’;

@endcode

Security considerations:

 The strcpy function is easily misused in a manner which enables malicious users

to arbitrarily change a running program's functionality through a

buffer overflow attack.

@see bcopy()

@see memcpy()

@see memmove()

@publishedAll

@externallyDefinedApi

*/

/** @fn  strcasestr(const char *s, const char *find)

@param s

@param find

Refer to  strstr() for the documentation

@see memchr()

@see strchr()

@see strcspn()

@see strpbrk()

@see strrchr()

@see strsep()

@see strspn()

@see strtok()

@publishedAll

@externallyDefinedApi

*/

/** @fn  strcat(char *  s, const char *  append)

@param s

@param append

Note: This description also covers the following functions -

 strncat() 

@return   The strcat and strncat functions

return the pointer s.

  The strcat and strncat functions

append a copy of the null-terminated string append to the end of the null-terminated string s, then add a terminating ‘\\0’

The string s must have sufficient space to hold the result.

 The strncat function

appends not more than count characters from append, and then adds a terminating ‘\\0’

Examples:

@code

#include <string.h>

#include <stdio.h>

int main()

{

    char one[50] = {"\0"};              

    strcpy(one,"Hello");

    strcat(one," World");

    printf("Concatenated String %s

",one);

    return 0;   

}

@endcode

 Output

@code

Concatenated String Hello World

@endcode

Security considerations:

 The strcat function is easily misused in a manner

which enables malicious users to arbitrarily change

a running program's functionality through a buffer overflow attack. Avoid using strcat. Instead, use strncat or strlcat and ensure that no more characters are copied to the destination buffer

than it can hold. Note that strncat can also be problematic.

It may be a security concern for a string to be truncated at all.

Since the truncated string will not be as long as the original,

it may refer to a completely different resource

and usage of the truncated resource

could result in very incorrect behavior.

Example:

@see bcopy()

@see memcpy()

@see memmove()

@see strcpy()

@publishedAll

@externallyDefinedApi

*/

/** @fn  strchr(const char *s, int c)

@param s

@param c

Note: This description also covers the following functions -

 strrchr() 

@return   The functions strchr and strrchr return a pointer to the located character, or NULL if the character does not appear in the string.

  The strchr function locates the first occurrence of c (converted to a char)

in the string pointed to by s. The terminating null character is considered part of the string;

therefore if c is ‘\\0’

the functions locate the terminating ‘\\0’

 The strrchr function is identical to strchr except it locates the last occurrence of c.

Examples:

@code

#include <string.h>

#include <stdio.h>

int main()

{

        char one[50];

        char* ret;

        strcpy(one,"abcd");

        ret = strchr("abcd", 'c');

        if(!strncmp(one+2,ret,1)) printf("\ 'c\ ' found in string \"abcd\"

");

        ret = strchr(one, 'z');

        if(ret == NULL) printf("\ 'z\ ' not found in string \"abcd\"

");               

        return 0;

}

@endcode

 Output

@code

 ’c’ found in string "abcd"

 ’z’ not found in string "abcd"

@endcode

@see memchr()

@see strcspn()

@see strpbrk()

@see strsep()

@see strspn()

@see strstr()

@see strtok()

@publishedAll

@externallyDefinedApi

*/

/** @fn  strcmp(const char *s1, const char *s2)

@param s1

@param s2

Note: This description also covers the following functions -

 strncmp() 

@return   The strcmp and strncmp return an integer greater than, equal to, or less than 0, according 

to whether the string s1 is greater than, equal to, or less than the string s2.

  The strcmp and strncmp functions

lexicographically compare the null-terminated strings s1 and s2.

 The strncmp function

compares not more than len characters.

Because strncmp is designed for comparing strings rather than binary data,

characters that appear after a ‘\\0’

character are not compared.

Examples:

@code

#include <string.h>

#include <stdio.h>

int main()

{

   char str1[]  = "abcdefg";

   char str2[] =  "abcdefr";

   int result;

   printf( "Compare '%s' to '%s

", str1, str2 );

   result = strcmp( str1, str2);

   if( result < 0 )

      printf( "str1 is less than str2.

" );

   else if( result == 0 )

      printf( "str1 is equal to str2.

" );

   else if( result > 0 )

      printf( "str1 is greater than str2.

" );

   printf( "Compare '%.6s' to '%.6s

", str1, str2 );

   result = strncmp( str1, str2, 6 );

   if( result < 0 )

      printf( "str1 is less than str2.

" );

   else if( result == 0 )

      printf( "str1 is equal to str2.

" );

   else if( result > 0 )

      printf( "str1 is greater than str2.

" );

   return 0;    

}

@endcode

 Output

@code

Compare ’abcdefg’ to ’abcdefr

str1 is less than str2.

Compare ’abased’ to ’abcdef

str1 is equal to str2.

@endcode

@see bcmp()

@see memcmp()

@see strcasecmp()

@see strcoll()

@see strxfrm()

@publishedAll

@externallyDefinedApi

*/

/** @fn  strcoll(const char *s1, const char *s2)

@param s1   

@param s2      

  This function lexicographically compares the null-terminated strings s1 and s2 according to the current locale collation, if locale is set. 

  Calls strcmp and returns an integer greater than, equal to, or less than 0, to whether s1 is greater than, equal to, or less than s2 if C locale is set.

  Otherwise it will compare the strings according to the smartphone's locale collation.

Examples:

@code

#include <string.h>

#include <stdio.h>

#include <locale.h>

int main()

{

    int res;

    setlocale(LC_ALL,"ar_AE.ISO-8859-6");

    if(strcoll("abcde","abcde")==0)

       printf("Strings are same

");

    return 0;

}

@endcode

 Output

@code

Strings are same

@endcode

@return   This  function  returns  an  integer  less than, equal to, or

greater than zero if s1 is found, respectively, to  be  less  than,  to

match,  or be greater than s2, when both are interpreted as appropriate

for the current locale.

@see setlocale()

@see strcmp()

@see strxfrm()

@see wcscoll()

@publishedAll

@externallyDefinedApi

*/

/** @fn  strcpy(char *  from, const char *  to)

@param from

@param to

Refer to  stpcpy() for the documentation

@see bcopy()

@see memcpy()

@see memmove()

@publishedAll

@externallyDefinedApi

*/

/** @fn  strcspn(const char *s, const char *charset)

@param s

@param charset

@return   The strcspn function

returns the number of characters spanned.

  The strcspn function

spans the initial part of the null-terminated string s as long as the characters from s do not occur in string charset (it

spans the complement of charset). In other words, it computes the string array index in s of the first character of s which is also in charset, else the index of the first null character.

Examples:

@code

#include <string.h>

#include <stdio.h>

int main()

{

    printf("Number of characters present in s

 which are not in charset is %d",strcspn("abcde","df"));

    return 0;

}

@endcode

 Output

@code

Number of characters present in s

 which are not in charset is 3

@endcode

@see memchr()

@see strchr()

@see strpbrk()

@see strrchr()

@see strsep()

@see strspn()

@see strstr()

@see strtok()

@publishedAll

@externallyDefinedApi

*/

/** @fn  strdup(const char *str)

@param str

  The strdup function

allocates sufficient memory for a copy

of the string str ,

does the copy, and returns a pointer to it.

The pointer may subsequently be used as an

argument to the function free .

 If insufficient memory is available, NULL is returned and errno is set to ENOMEM .

Examples:

@code

#include <string.h>

#include <stdio.h>

int main()

{

    char* ptr;

    ptr = (char *)strdup("abcde");

    printf("Duplicated string %s

",ptr);

    ptr = (char *)strdup("Hello Hi");

    printf("Duplicated string %s

",ptr);

    return 0;   

}

@endcode

 Output

@code

Duplicated string abcde

Duplicated string Hello Hi

@endcode

@return   The  strdup()  function  returns a pointer to the duplicated string, or

NULL if insufficient memory was available.

@see free()

@see malloc()

@publishedAll

@externallyDefinedApi

*/

/** @fn  strndup(const char *old, size_t sz)

@param old

@param sz

  The strndup function

allocates sufficient memory for a copy

of the string old ,

does the copy of at most sz characters, and returns a pointer to it.

If old is longer than sz, only sz characters are copied and a terminating NULL is added.

The pointer may subsequently be used as an

argument to the function free .

 If insufficient memory is available, NULL is returned and errno is set to ENOMEM .

Examples:

@code

#include <string.h>

#include <stdio.h>

#include <stdlib.h>

int main()

{

    char* ptr;

    ptr = (char *)strndup("abcde",3);

    printf("Duplicated string %s

",ptr);

    ptr = (char *)strndup("Hello Hi",5);

    printf("Duplicated string %s

",ptr);

    free(ptr);

    return 0;   

}

@endcode

 Output

@code

Duplicated string abc

Duplicated string Hello

@endcode

@return   The  strdup()  function  returns a pointer to the duplicated string, or

NULL if insufficient memory was available.

@see free()

@see malloc()

@publishedAll

@externallyDefinedApi

*/

/** @fn strnlen(const char *s, size_t len)

@param s

@param len

@return The  strnlen function returns strlen(s), if that is less than len, or len if there is no "\\0" character among the first len characters pointed to by s.

Examples:

@code

#include <string.h>

#include <stdio.h>

int main()

{

    char one[50];

    int ret;

    strcpy(one,"abcdef");

    ret = strnlen(one,5);

    printf("Length obtained using strnlen = %d\n",ret);

    ret = strnlen(one,10);

    printf("Length obtained using strnlen = %d\n",ret);

}

@endcode

 Output

@code

Length obtained using strnlen = 5

Length obtained using strnlen = 6

@endcode

Feedback For additional information or queries on this page send feedback

@publishedAll

@externallyDefinedApi

*/

/** @fn  strerror(int num)

@param num

Refer to  perror() for the documentation

@see intro()

@publishedAll

@externallyDefinedApi

*/

/** @fn  strerror_r(int errnum, char *strerrbuf, size_t buflen)

@param errnum

@param strerrbuf

@param buflen

Refer to  perror() for the documentation

@see intro()

@publishedAll

@externallyDefinedApi

*/

/** @fn  strlcat(char *dst, const char *src, size_t size)

@param dst

@param src

@param size

Refer to  strlcpy() for the documentation

@see snprintf()

@see strncat()

@see strncpy()

@publishedAll

@externallyDefinedApi

*/

/** @fn  strlcpy(char *dst, const char *src, size_t size)

@param dst

@param src

@param size

Note: This description also covers the following functions -

 strlcat() 

@return   The strlcpy and strlcat functions return the total length of the string they tried to

create.

For strlcpy that means the length of src .

For strlcat that means the initial length of dst plus

the length of src .

While this may seem somewhat confusing it was done to make

truncation detection simple. Note however, that if strlcat traverses size characters without finding a NULL, the length of the string is 

  considered to be size and the destination string will not be NULL-terminated (since there 

  was no space for the NULL). This prevents strlcat from running off the end of a string. In practice this should 

  not happen (as it means that either size is incorrect or that dst is not a proper "C" string). The check exists to prevent potential security problems in incorrect 

  code.

  The strlcpy and strlcat functions copy and concatenate strings respectively. They are 

designed to be safer, more consistent, and less error prone replacements for strncpy and strncat. Unlike those functions, strlcpy and strlcat take the full size of the buffer (not just the length) and guarantee 

to NULL-terminate the result (as long as size is larger than 0 or, in the case of strlcat , as long as there is at least one byte free in dst ). Note that you should include a byte for the NULL in size . Also note that strlcpy and strlcat only operate on true "C" strings. This means that for strlcpy src must be NUL-terminated and for strlcat both src and dst must be NULL-terminated.

 The strlcpy function copies up to size - 1 characters from the NULL-terminated string src to dst , NULL-terminating the result.

 The strlcat function appends the NULL-terminated string src to the end of dst . It will append at most size - strlen(dst) - 1 bytes, NULL-terminating the result.

Examples:

 The following code fragment illustrates the simple case:

@code

char *s, *p, buf[BUFSIZ];

...

(void)strlcpy(buf, s, sizeof(buf));

(void)strlcat(buf, p, sizeof(buf));

@endcode

 To detect truncation, perhaps while building a pathname, something

like the following might be used:

@code

char *dir, *file, pname[MAXPATHLEN];

...

if (strlcpy(pname, dir, sizeof(pname)) >= sizeof(pname))

        goto toolong;

if (strlcat(pname, file, sizeof(pname)) >= sizeof(pname))

        goto toolong;

@endcode

 Since we know how many characters we copied the first time, we can

speed things up a bit by using a copy instead of an append:

@code

char *dir, *file, pname[MAXPATHLEN];

size_t n;

...

n = strlcpy(pname, dir, sizeof(pname));

if (n >= sizeof(pname))

        goto toolong;

if (strlcpy(pname + n, file, sizeof(pname) - n) >= sizeof(pname) - n)

        goto toolong;

@endcode

 However, one may question the validity of such optimizations, as they

defeat the whole purpose of strlcpy and strlcat .

As a matter of fact, the first version of this manual page got it wrong.

Examples:

@code

#include <string.h>

#include <stdio.h>

int main()

{

    char one[50] = {"abcdefgh"};

    printf("String before strcpy %s

",one);

    strlcpy(one,"Hello");

    printf("String after strcpy %s

",one);

    strlcpy(one + 5, " ",1);

    strlcpy(one + 6, "World",5);

    printf("String after strncpy %s

",one);

    return 0;

}

@endcode

@see snprintf()

@see strncat()

@see strncpy()

@publishedAll